1972 Mercury 500 50 HP

[64Amphicar]

Hello all, I am working on a 1972 Mercury 500 50 HP outboard. I am trying to get it running, but not been having any luck with getting an spark. I do not see a coil on it any where. Also no wiring to the ignition driver. Any one have any advise on these engines? The serial # is 3096872 or 3096372 not sure if it an 8 or a 3 The grey wire attached to the side is spliced to the orange wire from the wiring harness

 

[64Amphicar]

Upon looking further I do not see a switch box on this motor either. At this point I am not sure if it a 1972 engine?? Also does any one know the wiring positions for the key switch?

 

[GA_Boater]

Let's get the right motor first. Your serial number is for 1971, but you have a 4D-5 magneto. A '71 has an ignition driver and switch box and no magneto.

You may have an older powerhead. Is there a serial number stamped below the timing pulley?

 

[racerone]

---The drive belt is not broken ?----Follow the wire from the cap to the coil.----It may not look like a traditional coil.-----Then again perhaps the distributor was replaced with a magneto from an earlier motor and the coil is inside.----Or the block was replaced.-----Bring it over or post some pictures of this fine machine.----If it is the magneto then you simply remove the bottom part.( 3/8" wrench and 4 screws ) to do that.-----Then carefully find the breaker points and clean them.-----Set them at 0.010".----Work carefully as those parts are expensive.

 

[64Amphicar]

Let's get the right motor first. Your serial number is for 1971, but you have a 4D-5 magneto. A '71 has an ignition driver and switch box and no magneto.

You may have an older powerhead. Is there a serial number stamped below the timing pulley?

View attachment 330868

That # is 2106695 I was given this engine and was told it was a 1972, I do not about the year, just want to get it running.

 

[GA_Boater]

SN 2106695 falls in the 1967 range;



The wiring diagram,which includes the key switch;



Racerone's advice about expensive parts is all too correct. A Merc magneto ignition is simple and reliable, but parts are harder and harder to find with matching prices.

 

[64Amphicar]

---The drive belt is not broken ?----Follow the wire from the cap to the coil.----It may not look like a traditional coil.-----Then again perhaps the distributor was replaced with a magneto from an earlier motor and the coil is inside.----Or the block was replaced.-----Bring it over or post some pictures of this fine machine.----If it is the magneto then you simply remove the bottom part.( 3/8" wrench and 4 screws ) to do that.-----Then carefully find the breaker points and clean them.-----Set them at 0.010".----Work carefully as those parts are expensive.

I am not sure what I have, there is no coil or switch box on this engine. It was given to me and all I know is from what I have been finding online. The only wire to the distributor/magneto/ignition driver is the grey one that has been spliced to an orange one coming from the wiring harness. Any and all advise is greatly appreciated.

 

[racerone]

The coil is INSIDE that magneto assembly !!----An elegantly simple / reliable device it is.-----You have to learn how to work on this machine as you will be shocked at the cost of work at a shop !!

 

[64Amphicar]

SN 2106695 falls in the 1967 range;

View attachment 330874

The wiring diagram,which includes the key switch;

View attachment 330875

Racerone's advice about expensive parts is all too correct. A Merc magneto ignition is simple and reliable, but parts are harder and harder to find with matching prices.

That looks like what I have, now I need to figure out the wiring at the ignition switch. The diagram above shows A B C D E F my ignition switch has M B M C A I and wiring harness has RED, YELLOW,WHITE,GREY, BLACK, BROWN and ORANGE wires. All have been disconnected so I am not sure which wire goes where. Thank again for all the information.

 

[GA_Boater]

Post a picture of your remote control.

 

[64Amphicar]

Post a picture of your remote control.

The ignition switch is mounted on the dash, not in the remote control. Looks like the throttle/shifter lever has been replaced with an after market one. It is dark here, but I can get some pictures tomorrow.

 

[racerone]

Remove the ONE wire ( gray ) from the magneto.----Now test for spark.----Do not apply 12 volts to this magneto.----Any smoke resulting from that will be expensive.----The magneto does not need 12 volts to make spark.

 

[64Amphicar]

Post a picture of your remote control.

Don't put words in my mouth. My words are asking for picture, not all that stuff about wiring.

 

[racerone]

Some how I think you have the wrong control box / ignition switch for what is installed on your motor now !!----The magneto does NOT need 12 volts to make spark.----Remove the one wire on the magneto and test for spark.----Not hard to do.-----You might as well consider removing the bottom half of this magneto ( 4 screws and a 3/8" wrench ) and easy job..----Need to clean and set breaker points at 0.010" .----No need to worry about timing. ----Most shops won't work on these simple magnetos anymore.----Best to learn this yourself.-----You will be saving lots of beer tokens that way.

 

[64Amphicar]

Some how I think you have the wrong control box / ignition switch for what is installed on your motor now !!----The magneto does NOT need 12 volts to make spark.----Remove the one wire on the magneto and test for spark.----Not hard to do.-----You might as well consider removing the bottom half of this magneto ( 4 screws and a 3/8" wrench ) and easy job..----Need to clean and set breaker points at 0.010" .----No need to worry about timing. ----Most shops won't work on these simple magnetos anymore.----Best to learn this yourself.-----You will be saving lots of beer tokens that way.

I was given this pontoon with this engine mounted on it. It had an Evinrude 40hp on it before. The pontoon is a 1995 Tracker. He had replaced all the wiring harnesses with Mercury wiring harnesses for this engine. The ignition switch is also aftermarket. I have the Red(Battery) wire attached to the B terminal, Orange (Magneto)to the I Terminal, Yellow( Starter Solenoid) to the Y terminal and the Black (ground) to M Terminal. I now have power to the Orange wire (Magneto) that stays on when the key is in the ON Position. I believe the Gray and White are for the choke and Brown for the Tach. Should I now attach the Orange wire to the Magneto and see what happens?

 

[64Amphicar]

 

[racerone]

I have clearly stated that the MAGNETO does not need 12 volts in order to make spark.------Post a video of possible smoking if you continue with your approach.

 

[64Amphicar]

I have clearly stated that the MAGNETO does not need 12 volts in order to make spark.------Post a video of possible smoking if you continue with your approach.

I realize that, that is why I am asking these questions about the wiring at the ignition switch. By putting the Orange wire (Magneto) on the I Terminal at the ignition switch, I have power to the magneto wire when the ignition switch is in the on position. Is this right??

 

[racerone]

No it is not ------The magneto does not need 12 volts.----The wire going to the magneto is put to ground to stop the engine.----That same circuit is OPEN in order for this magic magneto to produce spark !!-----Put that magneto on your work bench with not a single wire attached.-----Hook up a proper spark tester.----Spin it by hand.-----You would see spark like a small electrical storm.

 

[64Amphicar]

This is probably why the guy gave it to me, so I need to put that Orange wire on the Ground terminal at the ignition switch??